Complex mixtures of many thousands of defined sgRNA sequences—pooled CRISPR sgRNA libraries—are an important preclinical research tool. These CRISPR libraries enable disruption (or "knockout") of thousands of specific genes in a single experiment so as to identify specific genes required for a biological response and potential drug targets for disease phenotypes.

The first section of each sgRNA in these CRISPR libraries targets a particular gene so this region varies in each guide. However, the rest of the sgRNA sequence—the region that interacts with the Cas9 nuclease to catalyze knockout of the target gene—is the same in all guides throughout the library.

Cellecta used resources provided by this NIH grant to show that (1) modifications to this constant Cas9-binding region of sgRNA significantly improved the effectiveness of gene knockout with the CRISPR system and (2) CRISPR libraries containing these modified sgRNA sequences generate stronger and more robust results than those with standard sgRNA. These findings will help improve the effectiveness of these important research tools for drug target discovery.

Dr. Donato Tedesco, senior scientist at Cellecta and the lead scientist on this study expressed his excitement about the findings by noting that, "The results of this work are actually very practically useful since they provide an approach to improve the effectiveness of any sgRNA regardless of the gene it targets. A few modifications of the constant region of the sgRNA produce a marked increase in the rate of CRISPR-mediated gene knockout and significantly increase the strength of the data signal in a genetic screen."

Cellecta has already implemented the modified sgRNA design for constructing new CRISPR libraries and incorporated the improved design in its genome-wide CRISPR libraries. Moving forward, Cellecta plans to expand on this work and analyze other guide modifications and related improvements in CRISPR library design that are expected to help eliminate false positive results while increase the sensitivity of genetic screens.

About Cellecta: Cellecta, Inc., a leading provider of genomics products and services, focuses on RNAi and CRISPR technologies for the discovery and characterization of novel therapeutic targets, and genetic profiling for biomarker discovery. The well-cited functional genomics portfolio offers gene knock-out and knock-down screens, custom and genome-wide RNAi and CRISPR libraries, cell engineering, RNAi and CRISPR construct services, and mutation and expression profiling of cancer samples.